<!DOCTYPE html>
<meta charset="utf-8">
<link rel="match" href="relative_position_clip_ref.html">
<style>
body, html {
    margin: 0;
}
#a {
    overflow: hidden;
}
#b {
    background: lightgray;
    position: relative;
    left: 50%;
    transform: translateX(-50%);
}
</style>
<div id=a><div id=b>X

